5.4 The ratio of males to females in humans is not 1:1 Ms. Giraldo

According to segregation of the sex chromosomes during meiosis, the probability of an X sperm fertilization an egg is the same as a Y sperm fertilizing an egg. Should be 1:1

Heterogametic sex - An organism that has different sex chromosomes for each biological sex of the species. Assumptions: o BOTH types of gametes are equally successful in fertilization. o BOTH sexes are equally viable during development. o The surface of the egg is equally receptive to both X and Y gametes. The male to female ratio should be 1:1. This is not the case. Additional assumptions: o The Y sperm is lighter (100 million bp lighter) and reaches the egg quicker than the X sperm. o The female reproductive mucus may support/limit the passage of one gamete vs. another.

Primary sex ratio: Conceived. (Fertilization) Secondary sex ratio: Born much easier to determine product. Varies from country to country.

WHO Gender and Genetics Discussion Discussion questions 1.In the groups you are assigned, select a RECORDER that will copy down the questions, take notes, and write down the answers to the questions. 2.Make sure each group member’s name is at the top of the paper. 3.Stick to the discussion questions while in your small group. 4.Respect each other’s opinions within the group. Please be respectful

1.Discuss within your group how gender is identified in other countries/cultures? How do you think our country defines gender? Is this changing? 2.Is there any scientific evidence of the ‘gay gene’? Do you think researchers should continue to look for evidence? How will this benefit the LGBT community? 3.What are your thoughts about the sex selection across the globe? 4.Discuss the ABC News segment we watched about sex selection in India. What are your thoughts/opinions on the segment? Why do you think males are favored in countries like India and China? What will the long-term impact be on those countries? 5.In South America it is only legal to abort if a mother has been raped or if there is potential harm to the mother. If a fetus is found to have a genetic disorder, it is illegal for the mother to have an abortion. What are your thoughts? Should a mother in this situation have the right to abort? 6.Why do you think it is difficult to collect data on unsafe abortions?